The present invention relates to structures that protect organic optoelectronic devices from species in the surrounding environment.
Organic optoelectronic devices, including circuits, such as organic light emitting diodes, organic electrochromic displays, organic photovoltaic devices and organic thin film transistors, are known in the art and are becoming increasingly important from an economic standpoint.
As a specific example, organic light emitting devices (xe2x80x9cOLEDsxe2x80x9d), including both polymer and small-molecule OLEDs, are potential candidates for a great variety of virtual- and direct-view type displays, such as lap-top computers, televisions, digital watches, telephones, pagers, cellular telephones, calculators and the like. Unlike inorganic semiconductor light emitting devices, organic light emitting devices are generally simple and relatively easy and inexpensive to fabricate. Also, OLEDs readily lend themselves to applications requiring a wide variety of colors and to applications that concern large-area devices. In general, two-dimensional OLED arrays for imaging applications are known in the art and are typically composed of a plurality of OLEDs (one or more of which forms a pixel) arranged in rows and columns. Each individual OLED in the array is typically constructed with a first transparent anode (such as ITO), an organic electroluminescent layer on the first electrode, and a metallic cathode on the organic electroluminescent medium. Other OLED architectures are also known in the art such as transparent OLEDs (transparent cathode contact), and inverted OLEDs. Substrate materials may include glass, plastic, metal foil, silicon wafers, etc.
In forming an OLED, a layer of reactive metal is typically utilized as the cathode to ensure efficient electron injection and low operating voltages. However, reactive metals and their interface with the organic material are susceptible to oxygen and moisture, which can severely limit the lifetime of the devices. Moisture and oxygen are also known to produce other deleterious effects. For example, moisture and oxygen are known to increase xe2x80x9cdark spot areasxe2x80x9d in connection with OLEDs. Components of various other organic optoelectronic devices (e.g., organic electrochromic displays, organic photovoltaic devices and organic thin film transistors) are likewise susceptible to attack from exterior environmental species, including water and oxygen.
The above and other challenges are addressed by the present invention.
According to an embodiment of the present invention, an organic optoelectronic device structure is provided which comprises the following: (a) an organic optoelectronic device selected from an organic light emitting diode, an organic electrochromic display, an organic photovoltaic device and an organic thin film transistor; (b) first and second barrier layers, at least one of the first and second barrier layers permitting transmission of light between the an outer environment and the organic optoelectronic device; (c) a sealing region disposed between the first and second barrier layers, the sealing region cooperating with the first and second barrier layers to enclose the optoelectronic device and restrict transmission of water and oxygen from an outer environment to the optoelectronic device, the sealing region also having at least one associated material that is harmful to the optoelectronic device; and (d) a blocking region that is disposed between the first and second barrier layers and is also disposed between the sealing region and the optoelectronic device, the blocking region restricting transmission of the at least one associated material from the sealing region to the optoelectronic device.
Preferably, the sealing region is a material that undergoes a fluid-to-solid phase transformation. More preferably, the sealing region is selected from low viscosity epoxies, solders and two-part epoxies.
Preferred blocking regions are curable liquid adhesive and solid adhesive compositions. More preferred are thermally curable epoxies, ultraviolet-curable epoxies and two-sided adhesive tapes.
The first and second barrier layers are preferably comprise (a) glass, (b) metal, (c) silicon, and/or (d) a combination of a polymer substrate sub-layer with a plurality of cooperative barrier sub-layers disposed on the polymer substrate sub-layer. In the latter instance, the cooperative barrier sub-layers preferably comprise one or more planarizing sub-layers and one or more high-density sub-layers. More preferably, the cooperative barrier sub-layers comprise an alternating series of two or more planarizing sub-layers and two or more high-density sub-layers.
One advantage of the present invention is that organic optoelectronic structures are produced, which structures are protected by an effective barrier between the organic optoelectronic device and the ambient atmosphere, reducing the adverse effects of chemical species in the ambient atmosphere, such as moisture and oxygen.
Another advantage of the present invention is that sealing compositions having associated materials that adversely affect organic optoelectronic device performance can nonetheless be utilized in the construction of organic optoelectronic structures.
These and other embodiments and advantages of the present invention will become readily apparent to those of ordinary skill in the art upon review of the disclosure to follow.